Forming films on a substrate by chemical reaction of gases is one of the primary steps in the fabrication of modern semiconductor devices. These deposition processes include chemical vapor deposition (CVD) as well as plasma enhanced chemical vapor deposition (PECVD), which uses plasma in combination with traditional CVD techniques. CVD and PECVD dielectric layers can be used as different layers in semiconductor devices. For example, the dielectric layers may be used as intermetal dielectric layers between conductive lines or interconnects in a device. Alternatively, the dielectric layers may be used as barrier layers, etch stops, or spacers, as well as other layers.
Chemical precursors have been introduced into a substrate processing region of a substrate processing chamber. A substrate is positioned within the substrate processing region and one or more precursors may be introduced into the substrate processing region to deposit the film. Liquid precursors may be used by “bubbling” a carrier gas through the liquid to carry vapor into the substrate processing region. The effectiveness of this technique is dependent upon the vapor pressure of the liquid. The temperature of the liquid may be increased to increase the vapor pressure. An ultrasonic generator has also been used to generate droplets to increase the delivery of precursors to the substrate processing region, however, the droplet size can negatively impact deposition uniformity and gapfill capabilities.
Methods are needed to decrease the droplet sizes in aerosol-assisted CVD to broaden the available applications which can utilize low vapor pressure precursors.